Influence of bolts bending on the strength of flanges joints of pressure vessels

This paper highlighted the shortcomings of the current international normative on the calculation of flanges joints with gasket situated inside the circle of bolts holes. The current codes do not take into account, when calculating the flanged joints of the vessels, the bending stress that occurs as a result of the movement of the plates of the joint subjected to internal pressure. The bending of the bolts influences the deformation of the sealing gasket and – namely – the sealing of the flange joint. The knowledge of the bolts bending stresses allows to increase the time between two revisions/repairs and – namely – the useful life of the sealing gasket. The experimental data, obtained with the help of a strain gage bridge and by the Digital Image Correlation method on the designed experimental installation, highlighted the bending of the flange bolts, both for pressurization and depressurization. The experiments were performed at an internal pressure of 0.5; 1.0; 1.5 and 2.0 MPa.